Slide 1 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED The Global Positioning System as a Space Weather Monitor S.K. Morley 1, J.P. Sullivan 1, M.G. Henderson 1, J.B. Blake 2, D.N. Baker 3 1- Los Alamos National Laboratory, 2- Aerospace Corporation 3- LASP, U. Colorado

Slide 2 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED CXD: 19 on orbit, 6 orbital planes From Tuszewski et al., 2004.

Slide 3 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED Energetic Particle Sensors on CXD Photo: LA-UR , Friedel & Cayton, ESWW6, HXP LEP LEP: Low Energy Particle subsystem has 5 electron channels HXP: High-energy X-ray and Particle subsystem has 7 electron channels Eleven electron channels on 19 block IIR and IIF satellites

Slide 4 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED CXD counts show SI drive dropouts From Morley et al., 2010

Slide 5 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED CXD: 118 satellite-years of data! CXD-equipped

Slide 6 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED Previous work used up to 7 CXDs CXD-equipped

Slide 7 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED Where are Van Allen Probes and CXD? MLT - L MLat - L ns65 RBSP-A

Slide 8 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED Conjunction: RBSP & GPS within 1000km 140 conjunctions All at L~4, equatorial

Slide 9 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED Comparing counts with counts For each CXD channel, i –Van Allen Probes energy spectrum used to estimate “expected counts”, C, by folding with CXD response functions, G i

Slide 10 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED CXD counts vs “expected” counts Confirms that instrument responses are well-modelled

Slide 11 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED CXD counts are as “expected” 3x (dark) 2x (light)

Slide 12 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED Flux: Forward modelling Constrained fit using: –3 Maxwell-Juttner distributions, in E –1 Gaussian distribution in log(p) Multi-parameter fits performed using TMinuit in CERN’s ROOT package –Minimizer is variant of Davidon-Fletcher-Powell method –Minimizes MSE of counts from estimated flux spectrum

Slide 13 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED Sample Flux Comparisons Energy spectra can be far from Maxwellian in the heart of the radiation belt Data points – RBSP Red: MagEIS Black: REPT Curves – CXD fitted spectra Black: Total Red/Magenta/Green: M-J Blue: Gaussian

Slide 14 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED CXD fluxes close to “gold standard” 0.35 MeV0.73 MeV

Slide 15 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED CXD fluxes close to “gold standard” 1.00 MeV1.55 MeV

Slide 16 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED CXD fluxes close to “gold standard” 2.60 MeV3.40 MeV

Slide 17 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED Typically within factor of 2 3x (dark) 2x (light)

Slide 18 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED RBSP: March 17 th 1MeV

Slide 19 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED CXD: March 17 th 1MeV

Slide 20 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA UNCLASSIFIED GPS is a unique Space Weather capability 19 CXD on orbit, more coming… More than 118 satellite-years of CXD data since 2001 Current data density allows new discovery CXD validated against Van Allen Probes CXD fluxes typically within factor of 2 of Van Allen Probes at conjunction